\ 



AGRICULTURAL BOTANY. 127 



tors, soil differences, altitude, exposure, etc., tliey were able to eliminate only 

 the first mentioned, still the differences in plant development ( corresix)nding 

 to changes in atmospheric content) at the several stations in different direc- 

 tions and at increasing distances from the main center of pollution are so defi- 

 nite as to leave little doubt that the dominant factor therein is the varying 

 quality of the atmosphere. 



On damage caused to vegetation by sulphurous and sulphuric acids in 

 the atmosphere, R. R. Tatlock and R. T. Thomson (Analyst, 39 {1914), No. 

 458, pp. 203-210). — Giving the results of observations and analyses of different 

 portions of several plants and of soils in different localities, the authors reach 

 the conclusion that the atmosphere even of cities consuming large quantities of 

 coal is acid only under very exceptional circumstances, and even then within 

 narrow limits. Injurious effects, when present, are strictly local, neither 

 acidity nor damage being perceptible in cases where the acid has been dis- 

 persed through a large volume of surrounding air. 



Hail injury to cereals, R. Schander (Fuhling's Landw. Ztg., 63 {1914), No. 

 21-22, pp. 657-703, figs. 12). — Giving details and conclusions of a study of 

 hail injury to rye, wheat, barley, and oats, as regards the different parts and 

 stages, the author claims to have shown that certain forms of such injury may 

 be both qualitatively and quantitatively estimated by methods here exempli- 

 fied. 



Transpiration and the ascent of sap in plants, H. H. Dixon {London: 

 MacmiUan d Co., 1914, pp. VIII +216, figs. 30).— The author offers an explana- 

 tion of the ascent of sap in plants, based very largely on physical properties of 

 liquids. 



The transpiration stream, it is claimed, is raised by secretory actions taking 

 place in the leaf cells, or by evaporation and capillarity. The author main- 

 tains that structural and physiological evidence prevents the acceptance of 

 the physical or vital theories, as the same configuration, physical properties, 

 and structure of the wood indicate that water in the conducting tracts not 

 acted upon by force behind must pass into a state of tension. Therefore when 

 root pressure is not acting and when the leaves of trees are transpiring, the 

 cohesion of their sap explains fully the transmission of the tension downward, 

 and consequently explains the rise of sap. In order to raise the transpiration 

 stream 100 meters in height a tension of 20 atmospheres would be required. 

 Studies of cohesion of sap indicate that It amounts to at least 200 atmospheres, 

 and consequently would be in no way overtaxed by this tension. The determi- 

 nation of the osmotic pressure of sap has been shown to be adequate to 

 resist transpiration tension. Other factors, however, are said to enter in, 

 and the pressures developed are much in excess of those demanded by trans- 

 piration. It is claimed that the stored energy set free by transpiration in 

 leaves is quite sufficient to do the work of secretion against the resistance of 

 the transpiration stream. 



Extreme alterations of permeability without injury, W. J. V. Osteehout 

 {Bot. Gaz., 59 {1915), No. 3, pp. 242-253, figs. 4). — ^As some investigators have 

 claimed that permeability is a relatively fixed property of cells while others 

 assume that there are reversible changes, the author has undertaken a series 

 of experiments with living tissues of Laminaria saccharina, determining the 

 permeability of the cells by their electrical resistance. 



The results obtained by the use of quantitative methods indicate that the 

 permeability of protoplasm may be greatly increased or diminished without 

 injury. A rapid alternation of increase and decrease did not produce injury. 



The problem of food movement in trees, S. B. Elliott {Forestry Quart., 

 12 {1914), ^0. 4, PP- 559-561, figs. 2). — ^An account is given of a young white 



